WORLD CIVILIZATION

Detailed explanation-1: -Eratosthenes made several important contributions to mathematics and science, and was a friend of Archimedes. Around 255 BC, he invented the armillary sphere. In On the Circular Motions of the Celestial Bodies, Cleomedes credited him with having calculated the Earth’s circumference around 240 BC, with a high precision.

Detailed explanation-2: -If we accept the account of Strabo that Eratosthenes measured the circumference of the earth as 252, 000 stadia, the circumference would be 24, 662 miles, and the polar diameter 7, 850 miles-only 50 miles short of the true polar diameter. This is considered to be one of the first great triumphs of scientific calculation.

Detailed explanation-3: -This illustration shows how Eratosthenes actually calculated the circumference of the Earth. At noon on the summer solstice, Eratosthenes measured the length of the shadow cast by a column of known height at Alexandria.

Detailed explanation-4: -He invented a system of longitude and latitude and made a map of the known world. He also designed a system for finding prime numbers-whole numbers that can only be divided by themselves or by the number 1. This method, still in use today, is called the “Sieve of Eratosthenes.”

Detailed explanation-5: -In the third century BCE, Eratosthenes, a Greek librarian in Alexandria, Egypt, determined the earth’s circumference to be 40, 250 to 45, 900 kilometers (25, 000 to 28, 500 miles) by comparing the Sun’s relative position at two different locations on the earth’s surface.